16.12.2009 - Einstein Podolsky Rosen Paradox I
Gilles Kuhn: hello and lol gaya Gaya Ethaniel: Hello everyone :) Elliot Gloster: Hello BrainCrave OHare: hello gaya Melchizedek Blauvelt: hi all Dali Waverider: hi folks Gilles Kuhn: well i will begin by stating the legalities so all will be recorded by the kgb pixelised cat to my right and diffuse in all kind of website and by participating you accept so Gilles Kuhn: and for a change before really beginning is there a physicist or mathematician here? TR Amat: I did part of a BSc in physics... Gilles Kuhn: well i mean uni degree ones Gilles Kuhn: i assume all of us know physics basic Dali Waverider: My BA is in Math, but really that's "Computer 'Science'" TR Amat: My maths was the real problem I had with my physics dgree. :) Gilles Kuhn: please BA ? I have not studied all scholar title in the world..... TR Amat: Batchelor of Arts? Dali Waverider: Bachelor of Arts. Liberal Arts Melchizedek Blauvelt: Bachelor of Arts I presume? Dali Waverider: 4-year degree Gilles Kuhn: ok candidacy i presume for my ref Gaya Ethaniel: I did BA in Art/Archaeology ... almost totally ignorant of physics :) Gilles Kuhn: ah no license TR Amat: My Masters degree is computing and human science related. Justine Rhapsody: My degree was social work. :) Birric Forcella: Well, the blind will be leading the blind . . . Gilles Kuhn: ok well i asked that because i feel a physicist would be more appropriate to introduce the subject Melchizedek Blauvelt: Same as the European "candidate" degree I presume Birric Forcella: But I could pinch hit . . . TR Amat: UK: BSc, MSc, PhD. TR Amat: I'd like a PhD someday... Gilles Kuhn: ok so let be clear i am not a physicist so i am less familiar with this stuff that the formers theme which mean it will be a collective work even before starting debating Melchizedek Blauvelt: Mainland Europe: Candidate, Licentiate, Dr. TR Amat: My physics is rather shakey... :) Gilles Kuhn: so first i assume all of us understand some basic of quantum mechanic (qm) like wave function( schrodinger ) and basically the problem of measurement Gilles Kuhn: and too heisenberg uncertainty principles Gilles Kuhn: if not i will begin to try to explain quickly those Birric Forcella: I know enough about the stuff to keep it going off completely into fairy land Gilles Kuhn: ok so let begin by the ultra basic but quick Gaya Ethaniel: ok Gilles Kuhn: qm is about elementary particle that have one property is that they are emitted by quanta (packet of particle) as planck theorised in order to solve the paradox of the black corp Birric Forcella: I meant to keep it from going off - probably Freudian slip Gilles Kuhn: that have i a one property* Gilles Kuhn: lol birric TR Amat: quantum is all about relatives. :) Gilles Kuhn: from this planck invented to the planck constant Gilles Kuhn: well einstein had some problems with that tr Gilles Kuhn: -to* Gilles Kuhn: the little problem with these particle like photon for example is that in certain experimental setting (two slit experience) they act like waves even if they are particle Gilles Kuhn: so even if you send one photon after another into a sufficiently small slit the result of the photon distribution detected after the slit is wave like Gilles Kuhn: worst if you use two slit you have even interference in the ""waves"" Gilles Kuhn: so we have a problem Gilles Kuhn: (anybody dont hesitate to stop me for a question or a precision ) Gaya Ethaniel: ok so far so good :) Gilles Kuhn: the problem was solve by schrodinger and other theorist by the creation of schrodinger equation that describe the wave function of any particle Gilles Kuhn: noted by the greek letter psi Gilles Kuhn: this equation describe fully the evolution of any particles Gilles Kuhn: but Gilles Kuhn: there is some problem if you take the point of view of classical physic Gilles Kuhn: one of the consequence of qm is the complementarity problem Gilles Kuhn: roughly (very roughly) if you observe something you disturb it Gilles Kuhn: in more technical time the instrument of observation eigen wave function will interact with what you observe wave function thus destroying the perfect state of before Sartre Placebo: hello everyone TR Amat: I thought another big problem is that QM doesn't distinguish between the past and future - the equations say both are equal? Birric Forcella wonders if anybody who doesn't understand it already will understand it . . . Gaya Ethaniel: Hello Satre :) Gilles Kuhn: (note please that a wave function describe statistical comportement not precise trajectories) TR Amat: Hence things on the quantum level don't have an "arrow of time"? Gilles Kuhn: i wonder that too birric Gilles Kuhn: well time after please ! Gaya Ethaniel: :) Gilles Kuhn: but indeed and you have the same problem in classical physic Gilles Kuhn: ok thus we have another very fundamental limitation deriving from the theory the famous heisenberg incertainty TR Amat: Causation doesn't seem to work at a quantum level, you just have things which are connected, not causal. I think... Birric Forcella: I think we should start with what brought this up in the first place last time - the question about what reality really is Gilles Kuhn: the easiest way is the equation : h (planck constant) must remain inferior or equal to the variation of velocity multiplied by the variation of position and thats true for any object Gilles Kuhn: one sec birric TR Amat: Entropy, and hence time, does seem to operate above the quantum level, "classical physics". Gilles Kuhn: so basically if you know where something is you cannot know is speed and vice versa inside the planck scale Gilles Kuhn: entropy is a thermodynamic concept and thermo is reduced by qm Birric Forcella: Yes, Gilles, I was going to just put that into a frame. Planck showed (for whatever reason) that there is a minimum energy quantum you can exert. The simplest way you can explain the paradox is that if you push something by a quantum, it has to move EXACTLY a certain distance. This means, in the space in between, the thing DOES NOT exist. Gilles Kuhn: yes that is the standard interpretation Gilles Kuhn: copenhague interpretation Birric Forcella: You can see the problem for our usual understanding of reality Gilles Kuhn: yes but then it become a metaphor of the problem Gilles Kuhn: and thats all what copenhague is about : instrumentalism if you cannot observe thus you cannot claim existence Gilles Kuhn: ok that are the very very basic of the qm Birric Forcella: Now the question is, WHERE is the thing? the answer turns out to be that it is within some kind of statistical cloud - statistically is is very likely in the place where you would think it is - but there is a finite probability that it is somewhere else - in fact, there is a possibility that it can be very far away, even at the other end of the universe Gilles Kuhn: question thus far ? Gilles Kuhn: yes we will address that later birric Birric Forcella: Okay - then carry on Gilles Kuhn: (actually you can ask if the ""thing "" really exist at all bbetween two measure....) Birric Forcella: What is important is that the smaller the thing, the bigger the paradoxical effect Birric Forcella: However, in principle, this even holds for regular objects like cats and bathtubs - if you look at them either in short enough a time - or if you wait for a LONG enough time for something very unlikely to happen Gilles Kuhn: ok now our friend albert einstein didnt liked at all ; indeed birric ; to see science reduced at its most fundamental level to a mere statistical thing that was unable to even state the existence of elementary particle between measure Gilles Kuhn: indeed birric it is only because the constant of planck is very very small that macroscopic effect are in the immense majority of case totally negligible Gilles Kuhn: but i could not measure the position of any of you knowing perfectly your speed below the value of planck constant Gilles Kuhn: so albert tried to show qm was incomplete and thats what the article we will study is about Gilles Kuhn: ok now we will see what are the epistemological premise expressed by the article i suppose most of you tried to read it its quite short but very dry and dense Gaya Ethaniel nods nods ^^;;; I bypassed all the maths. TR Amat: I'm not sure about the relevance of Plancks Contant - that operates on a far smaller scale than where QM kicks in? TR Amat: I'm not sure about the relevance of Plancks Contant - that operates on a far smaller scale than where QM kicks in? Gilles Kuhn: heisenberg incertainty is direct function of planck constant Gilles Kuhn: planck constant is the base of qm math treatment Dali Waverider: right Gilles Kuhn: if you look a bit inside the equation of the article you will see a lot of h it is planck constant Birric Forcella: Just parenthetically -- not to interrupt Gilles but to clarify - this is often misunderstood - the effect pertains to certain double values (non-communting properties- meaning things you can't simply multiply) - this means, for instance, speed (momentum) and position. But there are innumerable properties to which it also applies. Howeer - you can measure each SINGLE property with arbitrary exactness - you can measure, for instance, position completely exactly - however , in that case you won't know the speed. Or you can measure the speed exctly - but then you wont' know the position. Gilles Kuhn: thanks birric indeed Gaya Ethaniel: That was on the first page of the paper I think ... Birric Forcella: Sorry, I didn't get to read the paper . . . Gilles Kuhn: ok two big assumption of epr criter for judging a theory is corectness (by experience) and completeness Gaya Ethaniel: And assumption that nothing travels faster than light right? Gilles Kuhn: too bad birric i think you would enjoy it it is short for next session i hope you will do TR Amat: QM kicks in about 10-9, Planck's Constant is in all the equations, but, the Planck length is 10-35, and there is a strong tendancy for people (maybe me in this case) to get things mixed up. Gilles Kuhn: thats special relativity gaya lorentz poincarré group of transformation and if not explicitely stated in premise as it is experimentally very well confirmed and no doubted at all at the time indeed Gaya Ethaniel: ok Gilles Kuhn: right tr but we consider planck constant not lenghrt TR Amat: Yes. Birric Forcella: Again, for clarification -- Planck showed that energy in a body (any body) can only be increased by a certain amount at a time and not smoothly. That is the so-called quantum. It is extremely small. However, Anything, even you body, receives additional energy in multiples of exactly that quantum. So you do not receive energy in a smooth gradient, but in packets. However, since the quantum is so small, you usually don't realize it when you drive a car. However, a photon does feel every packet. But in theory, if you look fast enough, you also see how YOUR body gets its energy one packet at a time. Gilles Kuhn: again right birric ! Birric Forcella: Gilles, I know everything about EPR and Bell and Aspect and beyond. I studied it quite extensively. Birric Forcella: If you want, I can explain the math, too TR Amat: As I understand it, is is uncertain whether time is quantised? Gilles Kuhn: yes i remember you said so and was counting (rightly ) with your help Birric Forcella: Let's stick with the basics now - because I really think we should get to the implications for our understanding of reality Birric Forcella: Carry on, Gilles Birric Forcella: I'll try to fill in Gilles Kuhn: so let consider in depth the epistemic premise of the article : corectness and completness but reality too i quote "(for a theory to be complete) every element of the physical reality must have a counterpart in the physical theory" Birric Forcella: The physics is not half as interesting as the philosophy that follows from it Gilles Kuhn: consider the quote is a big big epistemological assumption ! Gaya Ethaniel: :) Gilles Kuhn: thus they proceed to examine what physical reality is Gilles Kuhn: their criterion assumed to be sufficient is in resume if you can predict the value of a physical quantity without disturbing the system then there is a element of physical reality corresponding to the say quantity Gilles Kuhn: they dont intend that to be exhaustive Birric Forcella: Again, let me elucidate. Most physical equations produce curves (mathematical) and it is assumed that if the theory is right, then the particles in reality move in the same curves in a one-to-one relationship. This is meant with everything must have a counterpart here (in theory) as well as there (in reality) - of course it's not all curves. So you need to find a theory that completely accounts for what you find in reality. Now if reality goes off the rail - as in QM - you obviously have a problem Gilles Kuhn: agaijn right birric but i will add one very important thing these assumption assume a position of extreme ontological realism in science Birric Forcella: Right, exactly Gilles Kuhn: they ask a theory not only to work in a limited way but to be perfect of all experience we can have Birric Forcella: Often also called "Representationalism" - since the physical language is assumed to exactly represent reality Gilles Kuhn: and that was indeed the target of einstein with relativity in the purest tradition of classical newtonian physics Gilles Kuhn: (i suggest as there is no much time left to continue now to discuss this point we will resume the article argument next week) TR Amat: Would you like to summarise? Gilles Kuhn: first observation all the subsequent argument rely entirely on that realism or representationalism if yu assume like bohr a instrumentalist position the problem that we will have dont disappear but is not so dramatic Gilles Kuhn: in other word if you accept that scientific theories can contradict each other which is the idea of relativism the epr paradox is only an interesting difficulty inside a peculiar theory and even there dont pose insurmountable problems Gilles Kuhn: but if you want a theory of everything the paradox we will study is a big big difficulty Gilles Kuhn: in one and perhaps the easiest manner of seeing it it violate the causality locality and speed of light limits Dali Waverider: hasn't science included such dualities? I'm thinking particle vs. wave, for example? TR Amat: If you accept that scientific theories are only consistent over a small 'area' (say, a range of scales) what does that imply? Gilles Kuhn: particle vs wave is all qm is about in resume Gaya Ethaniel: Do you mean this bit Gilles? On page 1, "It seems to us that this criteron, while far from exhausting all possible ways of recognizing physical reality, at least provides us ..." Gilles Kuhn: the micro world has exotic properties and our macro habits like using the word particle and envisioning a billar ball is not working Gaya Ethaniel: btw I meant page 2 before re: Birric's point ... Birric Forcella: Well, I will make the counterpoint to Gilles' position. I do think that physical theories cannot ultimately be contradictory - and that reality cannot ultimately be contradictory Birric Forcella: Howeer, I am fully aware of the current stand of things Gilles Kuhn: that bit gaya say that physical reality criterium they gave is not exhaustive you can recognise other criterium but not one that is in contradiction with the single they fgave Gaya Ethaniel: ok Birric Forcella: As a summary - Classial physics thought that ontic phenomena could be represented "all the way down" to the smallest detail with complete exactness Gilles Kuhn: yes birric exactly i know you would assume a realist position as you would have guessed my constructivist empiricist one Birric Forcella: The naive QM position (which was first hoped to pertain) was that for technical reasons (distrubing stuff, etc.) we can only represent up to a certain, very small level Birric Forcella: However, the current stand of things says that below a certain level things DO NOT HAVE A REPRESENTATION AT ALL Gilles Kuhn: qm in his classical interpretation is not realist it say our knowledge of certain things is bound to be limited Gilles Kuhn: exactly Birric Forcella: This is a fundamental problem. As Gilles will show us - particles DO NOT HAVE AN EXISTENCE IN ANY COMPREHENSIBLE FORM Birric Forcella: Well, that was exactly the question of EPR. Is it limited just technically - or fundamentally. Gilles Kuhn: well i will try to show that and will indeed focus on the very concept of "comprehensible" but that would be way way later as i propose to really plundge us into the tecnicality of the epr argument first Gilles Kuhn: so next week we will attack the plat de résistance of the article Birric Forcella: Okay, very good. Nice presentation Justine Rhapsody: yes thank you Justine Rhapsody: I appreciate your explanations Gilles Kuhn: thanks you all for coming and a very very special thanks to you birric your precision and developement were most enlighting Dali Waverider: thanks to both of you TR Amat: I encountered this New Scientist article, but, I don't know if it clarifies or makes things more muddy: http://www.newscientist.com/article/mg19025504.000-free-will--you-only-think-you-have-it.html Gilles Kuhn: so next week we will reconvene may i ask you to just try to read the article even like gaya without the math even if they are not so monstrous TR Amat: Thanks for QM explanation. Melchizedek Blauvelt: Thanks guys & gals, time to run to the next event! Gaya Ethaniel: Thanks :)